Factorio Server Updater

#!/usr/bin/python3

from json import load
from hashlib import sha1
from os import mkdir, listdir
from argparse import ArgumentParser
from shutil import copyfile, rmtree
from os.path import join, isfile, isdir

import requests

BLOCK_SIZE = 65535

MOD_DIR = "mods"

API_VERSION = 2
MODS_URL = "https://mods.factorio.com"
AUTH_URL = "https://auth.factorio.com"

USER_AGENT = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36"
TOKEN_FILE = "token.txt"

def download_file(url: str, filename: str) -> None:
    r = session.get(url, stream=True, params={"username": username, "token": token})
    with open(filename, 'wb') as f:
        for chunk in r.iter_content(chunk_size=2048):
            if chunk:
                f.write(chunk)

def hash_file(filename: str) -> str:
    hasher = sha1()
    with open(filename, "rb") as f:
        buff = f.read(BLOCK_SIZE)
        while len(buff) > 0:
            hasher.update(buff)
            buff = f.read(BLOCK_SIZE)
    return hasher.hexdigest()

if __name__ == "__main__":
    # setup arguments
    parser = ArgumentParser(description="A script to download Factorio mods according to a mod list")
    parser.add_argument("-i", "--in-file", type=str, default="mod-list.json", help="The mod list file to read from")
    parser.add_argument("-u", "--username", type=str, help="The username you use to log into mods.factorio.com")
    parser.add_argument("-p", "--password", type=str, help="The password you use to log into mods.factorio.com")
    # parse arguments
    args = parser.parse_args()

    # make sure the mod list file exists
    assert isfile(args.in_file), "The specified mod list file doesn't exist"

    # clear the mod directory if anything exists in it
    if len(listdir(MOD_DIR)) > 0:
        print("Clearing mod directory...")
        rmtree(MOD_DIR)

    # create the mod directory if it doesn't exist
    if not isdir(MOD_DIR):
        print("Creating mod directory...")
        mkdir(MOD_DIR)

    # create a requests session
    session = requests.session()
    # make sure our session makes requests with a valid user agent
    session.headers.update({"User-Agent": USER_AGENT})
    # log in and generate the token file
    token = None
    if not isfile(TOKEN_FILE):
        # set the username global
        username = args.username
        # send the login request
        response = session.post(AUTH_URL + "/api-login", data={"username": username, "password": args.password, "require_game_ownership": "True"}, params={"api_version": API_VERSION})
        # parse the JSON and grab the token
        response_json = response.json()
        # make sure the login was successful
        assert "token" in response_json, "Invalid credentials"
        # set the token global
        token = response_json["token"]
        # dump the token
        with open(TOKEN_FILE, "w") as f:
            f.write("%s:%s" % (username, token))
    else:  # load the cookies from a cookie jar
        # load the cookies from a file
        with open(TOKEN_FILE, "r") as f:
            (username, token) = f.read().split(":", 1)

    # grab the mod list from the mod-list.json file
    client_mod_list = load(open(args.in_file, "r"))
    # iterate through each mod in the list
    for mod in client_mod_list["mods"]:
        # make sure the mod isn't base and that it's enabled
        if mod["name"] != "base" and mod["enabled"]:
            # grab the info for the mod
            mod_info = session.get(MODS_URL + "/api/mods/" + mod["name"]).json()
            # get the latest release from the mod info
            latest_release = mod_info["releases"][-1]  # last element is the newest
            # the name of the mod's zip file
            mod_file_name = latest_release["file_name"]
            # the SHA-1 hash of the file
            mod_hash = latest_release["sha1"]
            # the URL to download the mod from
            mod_download_url = MODS_URL + latest_release["download_url"]
            # create the mod file path
            mod_download_path = join(MOD_DIR, mod_file_name)
            # print status
            print("Downloading %s to \"%s\"..." % (mod["name"], mod_download_path))
            # download the mod
            download_file(mod_download_url, mod_download_path)
            # verify the mod's hash
            assert mod_hash == hash_file(mod_download_path), "Invalid hash on %s" % (mod["name"])
    # copy the mod-list.json into the new mods folder
    copyfile(args.in_file, join(MOD_DIR, args.in_file))